The present invention generally relates to systems and methods for high throughput selection. In one aspect, cells are contained within gel droplets, and the cells may interact with the gel droplet in some manner, e.g., to form the gel and/or to degrade the gel. The interaction of cells with the gel droplet may result in some cells being contained within gel droplets and other cells not being contained within gel droplets, which may form the basis by which the cells are sorted. Such cells can be relatively rapidly sorted, e.g., on the basis of size, for example, using filtration, centrifugation, or other similar techniques. In some cases, unlike sorting techniques which can only sort one entity, such as droplets, at a time, such techniques can allow for more than one entity (and in some cases, relatively large numbers of entities) to be simultaneously sorted, dramatically increasing throughput.